Abstract

Subjects judged changes in the amplitude and/or frequency of a 100‐ms signal either within a trial (experiment one) or between trials (experiment two). Within‐trial changes featured roving levels and frequencies, whereas between trial changes were always from the same pool of four stimuli. The cost of making two judgments as opposed to only one was measured by comparing performance in the three conditions (judge amplitude, judge frequency, or judge both). The cost of roving levels and frequencies was measured by comparing performance between the two experiments. It was found that two judgments resulted in a decrease in performance only when the rove was not employed. This agrees with findings in the bimodal dual‐task suggesting that the cost of dividing attention is a result of the use of long‐term memory, and that the sensory‐trace does not incur a cost in the dual‐task. [Research supported by the Nat. Inst. of Health (NIDCD 07787), USA, Univ. of California, USA, and CNRS, France.]